Conventional Flux-switching Permanent Magnet Machine Research Articles

Analysis of Synergistic Stator Permanent Magnet Machine With the Synergies of Flux-Switching and Flux-Reversal Effects

Dual permanent magnet (PM) machines have attracted numerous interests due to the high torque density and compact volume <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.</i> This article investigates a synergistic PM machines with the synergies of flux switching and flux reversal effects. The flux-reversal and flux-switching PM (FSPM) flux paths circulate from two sides of the split teeth separately, which avoid the over-saturation with dual PM excitations. The preferred stator and rotor pole number is derived from a simplified analytical model and the influence of leading parameters is analyzed as design guidelines. Furthermore, the synergistic stator PM machine is optimized and compared with FSPM machines. It is revealed that the synergistic stator PM machine exhibits ∼20%, ∼10%, and ∼17% higher torque density than conventional FSPM machine, C-core FSPM machine, and E-core FSPM machine, respectively. Besides, good flux weakening capability is achieved with a larger inductance than conventional FSPM machine, and higher efficiency is obtained at both low-speed and high-speed operations. Finally, an experimental prototype is fabricated to validate the proposed concepts.

Principle Investigation and Performance Comparison of Consequent-Pole Switched Flux PM Machines

This article proposes a novel topology of consequent-pole switched flux permanent magnet (SFPM) machine with U-shaped permanent magnets (PMs) for torque improvement, which is attractive for traction applications. The proposed machine is geometrically derived from a conventional sandwiched SFPM machine by introducing airspace flux barriers and flat-type PMs. The proposed design can provide an effective circulating path for low-order field harmonics. This property is beneficial for torque capability enhancement. The machine topologies and operating principles are introduced first. Moreover, a magnetomotive force (MMF) permeance-based model for the proposed SFPM machines is employed to analytically reveal the underlying working mechanism. The electromagnetic characteristics of the two proposed SFPM machines are investigated by finite element (FE) analyses and compared with those of the conventional sandwiched SFPM machine. Finally, a 6-/13-pole SFPM machine with a U-shaped PM structure is manufactured and tested to experimentally validate the theoretical and FE analyses.

High Gear Ratio Flux Switching Permanent Magnet Machine for High Torque Performance

A high gear ratio flux switching permanent magnet machine (HFSPM) was proposed to improve the torque performance in flux switching permanent magnet machine (FSPM). Conventional FSPMs address flux bypass issue when designed with a high gear ratio. The HFSPM adopts a dual rotor structure to overcome this flux bypass issue. First, the cause and effect of flux bypass issue was discussed using a magnetic equivalent circuit (MEC). Further, the process of overcoming the flux bypass issue using dual rotor structure was discussed. An alternative HFSPM, consequent pole HFSPM (CP-HFSPM), was proposed to enhance torque performance. The CP-HFSPM was optimized for high torque performance and proper power factor.

Design and optimization of HTS flux-switching permanent magnet machine

&lt;p&gt;Flux-switching permanent magnet (FSPM) machine with high temperature superconductors (HTS) bulks located between the rotor poles to eliminate the flux leakage in the rotor, termed as (HTS-FSPM) machine has been proposed in this paper. Using genetic algorithm, the HTS and the conventional FSPM machines having the same size constraints and load conditions have been globally optimized for max. aveage torque. To highlight the advantages of the HTS-FSPM machine, a performance comparison between the conventional and HTS-FSPM machines has been presented. It is found that the HTS-FSPM machine can increase the torque by 27%, however, this comes with the expense of higher torque ripple and power losses. &lt;/p&gt;

Elementary Analysis of Segmental Stator Flux Switching Permanent Magnet Machine

&lt;span lang="EN-US"&gt;Segmental structure is common especially for a rotor in electrical motor. It is to reduce the cost of production, conveniently replace, and as a module where the sum of electromagnetic torque produced comes from each segmental stator add up together. Thus, in this paper will be focusing on the elementary analysis of a segmental stator for single phase 6Slot-12Pole and 3 phase 6Slot-15Pole Switched-Flux Permanent Magnet Machine (SFPMM) as the chosen design for analysis validation from coventional permanent magnet flux switching machine to a new segmental stator structure of SFPMM. It will be focusing on the initial design and to prove that it can be operate as a flux switching machine by implement a 2D Finite Element Analysis simulations such as a No-load analysis (flux linkage, cogging torque, back emf) and Load-analysis (average electromagnetic torque. Elementary result shows that the electromagnetic torque produce for both design are 10.6 Nm and 99.95 Nm and proved that it can produce high torque although it does not surpass the conventional SFPMM. A further research and optimization will be needed to obtain a higher torque compared to conventional SFPMM.&lt;/span&gt;

Dynamic performance of the novel axial flux-switching permanent magnet motor

PurposeThe purpose of this paper is to investigate a novel axial flux-switching motor with sandwiched permanent magnet for direct drive electric vehicles (EVs), in which the torque density is increased and the cogging torque is decreased. For reducing the back-electromotive force (EMF) harmonics and cogging torque, a twisted structure is employed. To improve the dynamic performance of the axial field flux-switching sandwiched permanent magnet (AFFSSPM) motor a space vector modulation-direct torque and flux control scheme is proposed.Design/methodology/approachA multi-objective optimization is performed by means of artificial neural network and non-sorting genetic algorithm II to minimize the cogging torque while preserving the average torque.FindingsA comparative study between two proposed machines and the conventional flux-switching permanent magnet (FSPM) machine is accomplished and the static electromagnetic characteristics are analyzed. It is demonstrated that the proposed model with twisted structure has significantly improved performance over the conventional FSPM machine in back-EMF and efficiency. The proposed controller has a speed loop only and contains neither the current loop nor hysteresis control. The AFFSSPM motor exhibits excellent dynamic performance with this scheme.Originality valueThe axial flux-switching permanent-magnet machine is one of the most efficient machines but the AFFSSPM with sandwiched permanent magnet has not been specially reported to date. Thus in this paper, the authors report on optimal design of an axial flux-switching sandwiched permanent magnet machine for electric vehicles and investigate its dynamic performance.

Concept of Integration of Axial-Flow Compression Into Electric Machine Design

The purpose of this paper is to propose a novel concept of a high-speed electric machine system with integrated airfoil-shaped rotor designed to perform axial-flow compression for vehicle applications. The proposed high-speed machine is both a motor for electromagnetic (EM) energy conversion and an axial flow compressor for thermodynamic energy conversion. Conventional designs usually have a separate motor and compressor that are connected through a common shaft with or without a gearbox. The proposed design simplifies the high-speed machine and compressor system by eliminating the components that connect the motor and the compressor. The integrated motor-compressor design can achieve a more compact system. The flux-switching permanent magnet (FSPM) machine is chosen out of several possible electric machine topologies with salient rotor pole features for the integrated motor design. The feasibility of this integrated motor-compressor design is discussed from both the EM and thermodynamic perspectives in this paper. The selection of slot/pole combination and EM sizing equations for the integrated FSPM motor-compressor are discussed. Mean-line design equations for the axial flow compressor are studied for the proposed integrated motor-compressor. The EM torque production capability of the proposed integrated motor-compressor is verified for one possible design in this paper by finite element analysis (FEA). The effects of two different attack angles of the rotor blades are studied compared to the conventional FSPM machine. The FEA results show that the proposed integrated motor-compressor achieves the expected output performances.

Novel switched flux machine with radial and circumferential permanent magnets

Purpose– The paper purposes a novel SFPM machine topology with radial and circumferential permanent magnets (PMs). The paper aims to discuss this issue.Design/methodology/approach– In order to reduce the flux leakage in the stator-outer region and consequently achieve higher magnetic material utilization in switched flux permanent magnet (SFPM) machine, a novel topology with radial and circumferential PMs is proposed. This topology (SFRCPM) has the same structure as conventional SFPM (CSFPM) machine except of the additional set of radially magnetized PMs located around the back iron and surrounded by a laminated ring frame. Using finite element analysis (FEA) the influence of the design parameters on the performance is investigated in order to obtain an effective optimization procedure. Internal and external rotor SFRCPM machines with either NdFeB or ferrite magnets are investigated, optimized and compared with the CSFPM machine having the same size, copper loss and stator/rotor pole combination.Findings– It is concluded that comparing SFRCPM with its CSFPM machine counterpart, internal rotor SFRCPM machine can achieve high PM flux-linkage per magnet volume, however reduced slot area leads to low output torque, whereas external rotor SFRCPM machine can produce higher torque and torque per magnet volume.Originality/value– This paper proposes a novel SFPM machine topology.

Synthesis of Flux Switching Permanent Magnet Machines

This paper investigates the nature of a flux switching permanent magnet (FSPM) machine based on the flux harmonic theory. First, analytical expressions for air-gap flux density distribution, back-electromagnetic force (EMF), and torque are developed to analyze the electromagnetic features of FSPM machines. It is found that the conventional winding theory, such as star of slots, can be directly employed to analyze FSPM machines without any modification. Combinations of stator and rotor teeth, winding connection, and conditions for symmetrical-phase back-EMF waveform are analyzed and obtained using star of slots. The armature winding pole pairs of FSPM machines are redefined. Based on this new concept and the proposed analytical expressions, slots per phase per pole and winding factor in FSPM machines are derived, a new type winding configuration with overlapping windings for FSPM machines is predicted and verified to be with ∼90% larger back EMF than those of conventional FSPM machines with nonoverlapping windings. All these analysis results are validated by finite element analyzes.

Design and Comparison of Two Six-Phase Hybrid-Excited Flux-Switching Machines for EV/HEV Applications

Multiphase flux-switching permanent-magnet (FSPM) machines inherit the merits of conventional FSPM machines and the common advantages of multiphase machines, e.g., low torque pulsations, a high torque density, and a high fault-tolerant capability. When a hybrid excitation is applied, postfault armature currents can be reduced by applying a positive field current (PFC). Hence, in this paper, based on both 2-D and 3-D finite-element analyses (FEAs), two six-phase hybrid-excited flux-switching (HEFS) machines with E-core and C-core stator laminations are designed, respectively. Iron bridges are adopted in each machine, and the influences on the performance are investigated. In addition, alternative-tooth-wound armature windings are employed in the C-core machine to obtain physical and magnetic isolations between armature phases. A comprehensive comparison of the two designs is carried out. Then, more attention is paid to fault-tolerant operating capabilities when an open-circuit fault occurs to only one phase and two phases of armature windings, respectively. The PFC can be applied in the C-core machine under fault-tolerant operating conditions; thus, the postfault armature current can be reduced while maintaining the torque output. Overall, the torque output can be effectively maintained in each HEFS machine during postfault operations. Finally, the FEA-based studies are validated by experimental measurements on two HEFS machine prototypes.

Comparative study of the electromagnetic performance of switched flux permanent magnet machines

Switched flux permanent magnet (SFPM) machines have significant potential for many industrial applications because of their doubly salient structure, similar to switched reluctance machines. In recent years, several novel SFPM machine topologies, such as multi-tooth, E-core and C-core, have been developed to reduce the usage of permanent magnet materials without sacrificing the torque capability. A comparative study of the electromagnetic performance of these topologies, together with conventional SFPM machines having different stator/rotor pole combinations, that is, 12/10, 12/13 and 12/14, is presented. In addition to open circuit and electromagnetic torque performance, their torque–speed characteristics are investigated and compared. It is found that for conventional SFPM machines, the higher the rotor pole number, the better the flux-weakening capability, and higher maximum speed can be achieved. In contrast, owing to high d-axis inductance in the multi-tooth, E-core and C-core machines, infinite maximum speed can be obtained. Moreover, among all these machines, the multi-tooth machine has the highest flux-weakening factor, while the E-core machine exhibits the largest power capability. In addition to two-dimensional (2D) finite-element analysis (FEA), 3D-FEA is also performed accounting for the end effect. Finally, the torque–speed characteristics of prototype SFPM machines are measured to verify the FEA.

Switched flux hybrid magnet memory machine

A novel switched flux permanent magnet machine (SFPMM) with both normal NdFeB and low coercive force (LCF) magnets has been developed in this paper. Outside a conventional SFPMM, the LCF magnets are mounted on the back of every U-shaped stator lamination segment with parallel magnetisation direction and alternative polarities. A lamination ring yoke is placed around all the LCF magnets, while extra magnetisation coils are wound on each of them. By injecting different directions of current pulses into the magnetisation coils, the polarities of the LCF magnets can be rewritten in order to enhance or weaken the field generated by normal NdFeB magnets. Therefore the back EMF and torque capability could be adjusted in a wide range. In this paper, the operation principle and machine topology are introduced firstly. Then the stator/rotor pole combinations and design considerations of the machine have been discussed. With the help of two-dimensional finite element software, a 6/5 stator/rotor pole machine has been globally optimised as an example to show the machine performances such as open-circuit field and back EMF, dq -axis inductances, torque capabilities and magnetisation. Finally, a prototype with the same dimensions has been manufactured and tested to validate the analysis results.

Modular Stator High Temperature Superconducting Flux-Switching Machines

Flux-switching permanent magnet (FSPM) machines have advantages of robust rotor, strong permanent magnet (PM) dissipation ability, etc, but its flux-weakening capability is poor for its constant PM flux linkage. High temperature superconducting (HTS) excitation windings can produce higher flux density than PM excitation and modify the airgap flux density easily. But if the HTS coils are placed adjacent to the armature winding in the same slot, the heat produced by the armature winding is difficult to cool down. In this paper, a modular stator HTS flux-switching (HTS-FS) machine is first proposed, and the operation principle is described in details. Second, mathematical equations are proposed and detailed electromagnetic design has been done. Then, the optimization of width of flux barrier, rotor pole arc and split ratio have been made to get higher back-EMF, higher output torque capability, and lower torque ripple. Moreover, the comparisons of key performance indexes between HTS-FS machine and conventional FSPM machines have been made. The results show that the HTS-FS machine can produce higher back-EMF than FSPM machine, and at small armature current, it can produce higher torque with little electromagnetic saturation.

Analysis of a Novel Switched-Flux Memory Motor Employing a Time-Divisional Magnetization Strategy

This paper presents a novel switched-flux memory motor (SFMM) by artfully incorporating the flux-mnemonic concept into the conventional switched-flux permanent magnet machine. The magnetic susceptibility of AlNiCo PM provides the flexible online controllability of air-gap flux by imposing a transient current pulse. To uniformize magnetization levels of PMs, a time-divisional magnetization strategy (TDMS) is proposed. Due to the uniqueness of hysteresis nonlinearity and instability regarding AlNiCo PM operating point, the time-stepping finite element method (TSFEM) dynamically coupled with a nonlinearity-involved parallelogram hysteresis model (NIPHM) of AlNiCo PM is performed to investigate the electromagnetic performance of the proposed SFMM. The results derived from the combinative algorithm verifies the flux-adjustable capability of the proposed motor equipped with TDMS and the validity of the proposed NIPHM.

High-Torque-Density High-Efficiency Flux-Switching PM Machine for Aerospace Applications

Recently, flux-switching permanent magnet (FSPM) machines have been increasingly investigated due to its torque density and fault tolerance. Because of this, they are attractive for aerospace applications where weight, installation spaces, and safety play a critical role. Recent research has investigated a variation of the conventional FSPM machine called the C-core FSPM machine, which offers 40% greater electromagnetic torque, while using half of the magnet mass. This paper proposes a new topology called Halbach-FSPM capable of achieving an electromagnetic torque 20% higher than the C-core FSPM machine, while maintaining machine volume and phase current constant and using no more magnet material than a conventional FSPM machine. First, a physical explanation of the advantages are developed for use in all FSPM machines using Halbach arrays. An analysis and comparison of torque, power and efficiency are made. Further, magnet losses and segmentation applicable to all FSPM topologies are discussed, plus an analysis on magnet usage is given.

New Axial Laminated-Structure Flux-Switching Permanent Magnet Machine With 6/7 Poles

In this paper, one new axially laminated-structure flux-switching permanent magnet machine (ALSFSPMM) with 6/7 (stator/rotor) poles is proposed. Different from the conventional flux-switching permanent magnet machine (FSPMM), the stator and rotor of ALSFSPMM are laminated parallel to the axial direction, which can make full use of PM flux linkage, decrease part magnetic saturation, and reduce the iron loss particularly in the range of high speed. By the 2-D model prediction of finite element algorithm (FEA), ALSFSPMM has lower cogging torque, stronger flux weakening ability, greater torque density, higher efficiency, etc., and hence it is an ideal candidate for the drive system of plug-in hybrid electrical vehicle (PHEV).

Influence of Slot Opening on Optimal Stator and Rotor Pole Combination and Electromagnetic Performance of Switched-Flux PM Brushless AC Machines

The significant influence of slot opening on the optimal stator and rotor pole combination and on the electromagnetic performance of the switched-flux permanent magnet (SFPM) machine is observed and investigated in this paper. A new SFPM brushless machine with remarkable slot opening relative to the magnet thickness is developed to reduce the magnet usage and to increase the slot area. Its stator slot opening is almost several times of that in the conventional SFPM machine, but its magnet usage is only half. However, the new machine exhibits ~ 40% larger back EMF and electromagnetic torque than those of the conventional machine, while its cogging torque and torque ripple are significantly lower.

A Novel Hybrid-Excited Switched-Flux Brushless AC Machine for EV/HEV Applications

A novel E-core hybrid-excited switched-flux permanent-magnet (SFPM) brushless machine is proposed based on an E-core SFPM machine, which has significantly less magnet and higher torque density than those of a conventional SFPM machine. The proposed machine has a simple structure. The main flux path of dc excitation does not affect the magnet excitation because it is not through magnets. The combination of stator and rotor pole numbers of the proposed machine is optimized, and the flux-enhancing and flux-weakening capabilities are investigated by 2-D finite-element analyses and experimentally validated.

Stator and Rotor Pole Combinations for Multi-Tooth Flux-Switching Permanent-Magnet Brushless AC Machines

A simple analytical method is developed for determining the optimal combination of stator pole and rotor pole numbers for a multi-tooth flux-switching permanent magnet (FSPM) machine, and the optimal design of the stator teeth for maximum torque. In addition, the rotor pole width and the split ratio are optimized by finite element analysis. The optimized multi-tooth FSPM machine exhibits a significantly higher torque capability and requires a significantly lower volume of magnet material than a conventional FSPM machine. The performance of the proposed multi-tooth FSPM machine is validated experimentally.